Root and alveolar bone status of maxillary labial inverted impacted incisor in mixed dentition after orthodontic treatment

Objective To study the alveolar bone surrounding situation and the length of the root of the maxillary labial inverted impacted incisor in mixed dentition after orthodontic treatment. Methods Fourteen cases with maxillary labial inverted impacted incisor in mixed dentition were collected. Modified Nance arch and conventional appliance were used. Cone-bean CT(CBCT) was taken after the treatment.Simplant13.0 three-dimensional reconstruction and multi-planer reconstruction(MPR) method were used to observe the labial and lingual alveolar bone crest morphology,besides,the labial and lingual length from the alveolar bone crest to cemento-enamel junction(CEJ) of the impacted incisor and the homonym tooth after treatment,along with their root length and their labial and lingual length ratio of the root surrounded by the alveolar bone to the total root length were measured.The idependent samples t-test were used to analyze the variable differences.Results The labial and lingual alveolar bone of fourteen cases crest of the diseased tooth after treatment presented general symmetry U shape from qualitative observation through the threedimensional reconstruction.The labial and the lingual length of the diseased incisor from alveolar bone crest to CEJ[ (2.47 ± 1.35) and ( 1.47 ± 0.84) mm] was significant increased than those of the homonym incisor[ ( 1.03 ± 0.35) and (0.90 ± 0.37 )mm ] ( P ＜ 0.05 ) ; the length of the diseased incisor's posttreatment root [ (9.82 ± 2.82) mm ] was no statistically significant decreased than that of the homonym incisor root[ ( 10.28 ± 1.38) mm,P =0.59] ; the labial and the lingual length ratio of the impacted tooth's root surrounded by the alveolar bone to the total root length[ (72.83 ± 17.16)％ and (85.32 ±5.98)％ ]was statistically significant decrease than those of homonym teeth [ ( 89.66 ± 3.98 ) ％ and ( 90.84 ±4.61 )％ ] (P ＜ 0.05 ). Conclusions The diseased tooth's root had gotten enough length after the treatment.The labial and lingual alveolar bone of the maxillary labial inverted impacted incisor in mixed dentition can't offer sufficient adaptive hyperplasia after treatment,of which labial alveolar bone is more apparent,prompting careful protection when they were used. Key words: Cone-beam computed tomography; Tooth, impacted; Alveolar bone loss; Incisor